1. Field of the Invention
The present invention relates to a data shuffling apparatus used in the recording or transmission of video information after high efficiency encoding.
2. Description of the Prior Art
The data quantity of video information is enormous, and accordingly, such information is often transmitted or recorded after effecting high efficiency encoding which reduces the data quantity. High efficiency encoding involves compressing the data quantity by removing redundant portions of the video information. As one method of high efficiency encoding, it is known, for example, to divide the input sample values into blocks composed of adjacent plural pixels, orthogonally transform the sample values in each block to obtain orthogonal transformation coefficients, and encode the orthogonal transformation coefficients. In such a block unit coding technique, it is first necessary to shuffle the input video data, or to rearrange the data into a sequence of blocks suited to encoding. In particular, shuffling of the blocks is important to enhance the coding efficiency or disperse the effects of error (see the Japanese Patent Application No. 63-271178).
Referring to FIG. 10, prior art example will now be described in which two fields (=1 frame) of TV signals are gathered to make up one page, and one block unit of data is composed of the signals from both fields. As shown in FIG. 10, such a block is composed of a total of 64 pixels, i.e., adjacent pixels from 4 horizontal lines by 8 vertical lines in each of two fields in a time axis direction. A conventional shuffling apparatus is shown in FIG. 11.
In FIG. 11, numeral 1 is a video input, 2 is an input switch, 3 is a first page memory, 4 is a second page memory, 5 is an output switch, 6 is a video output, and 7 is an address control unit. A TV signal is first entered beginning from the top line of the first field sequentially line after line, and after all lines of the first field are entered, the input of the second field is started. In FIG. 11, the video data entered from the video input 1 is input into the first page memory 3 by the input switch 2. At the same time, the video data of the previous page recorded in the second page memory 4 is shuffled, and delivered to the video output 6 through the output switch 5. Meanwhile, the input and output addresses of the two page memories 3, 4 are controlled by the address control unit 7, and are rearranged into blocks as shown in FIG. 10. In this way, when the input and output of the image data for one page is complete, the input switch 2 and output switch 5 are changed over, and the same processing is conducted using the first page memory as the output memory and the second page memory as the input memory. In this manner, by changing over the input and output memories, a continuously entered moving picture signal can be shuffled.
In this prior art apparatus, however, the shuffling of data in two fields (one page) requires video memories sufficient for four field (two pages). Thus, since the data quantity of video information is enormous, a large memory is required for shuffling, which results in an increase in both cost and power consumption.